Also played Eufloria a long time ago and there was another game that had similarities called Galcon which maybe had more in common with RISK. The developer had Galcon Fusion and Galcon Legends on Steam back then which I think supported multiplayer yet were largely singleplayer, but they were removed from the store after they released Galcon 2 which is aimed at cross-platform multiplayer.

* https://www.galcon.com/games/

* http://www.galcon.com/g2/

* https://store.steampowered.com/app/294160/Galcon_2_Galactic_...